Prevotella intermedia is associated with both oral (periodontal disease and endodontic infections) and extraoral infections. Despite this organism's association with disease little is known about the genetic or biochemical basis of its virulence. An essential step in establishment of an infection is the ability of a pathogen to multiply within its host. This property is greatly influenced by availability of nutrients such as iron. Hemin has been shown to be an indispensable nutrient for these bacteria. It serves as a source of iron and protoporphyrin IX. Thus, we will start our study of the virulence features of this bacterium by investigating the molecular mechanisms of hemin acquisition. First, we shall identify the genes involved in the pigmentation locus. In oral gram-negative bacteria, black pigmentation results from accumulation of hemin on the cell surface. We hypothesize that there are several genes coding for the proteins participating in the integration of hemin. Furthermore, we hypothesize that the genes involved in hemin/iron transport are coordinately regulated by iron. Proteomics is the best approach to rapidly identify large numbers of differentially regulated gene products. Using this approach we intend to identify proteins affected by iron depletion. The results of our study will help define iron uptake mechanisms that may serve as targets in the future design of antibacterial agents for P. intermedia. Since P. intermedia is resistant to many antibiotics alternative methods of preventive measures are needed for this bacterium.